Method and apparatus to measure amount of movement using granular speck pattern generated by reflecting laser beam

ABSTRACT

A granular speck pattern is generated by a reflecting laser beam as an object to be measured is irradiated with a laser beam. This granular speck pattern is directly picked up as image index by a line sensor. An A/D converter converts an analog signal supplied from the line sensor to a digital signal, a processing unit calculates the amount of movement of the object on the basis of movement of a pixel interval of the granular speck pattern. A display device displays the amount of movement calculated by said processing unit.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 09/838,905, filed Apr. 20, 2001, entitled METHOD AND APPARATUSTO MEASURE AMOUNT OF MOVEMENT USING GRANULAR SPECK PATTERN GENERATED BYREFLECTING LASER BEAM, now U.S. Pat. No. 6,847,910.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and an apparatus adapted tomeasure an amount by which an object to be measured has moved in planeand back-and-forth in non-contacting fashion at a high speed without ademand for particular index or mark substantially freely from conditionsof said object such as temperature, color or material thereof.

Irradiation of the object to be measured with a monochromatic laser beamhaving high directivity, high luminance and linearity generates agranular speck pattern upon its reflection. This granular speck patterndepends on a degree of roughness on the surface of the object irradiatedwith the laser beam. The granular speck pattern translates in proportionto expansion or extension as the object is heated or an external stressis exerted on the object. On the other hand, the granular speck patternis reduced or magnified as the object moves back-and-forth.

The present invention intends to pick up this granular speck pattern indirect and optical manner as an index, to calculate a movement of theobject with respect to said index and to display the calculated resultas the amount of movement.

2. Description of the Related Art

A non-contact method for such measurement is well known in which theobject is irradiated with a laser beam vertically to the object andthere are provided a pair of unidimensional sensors at an angle of 45°about the normal line, respectively.

Irradiation of the object with a laser beam results in generation of thegranular speck pattern due to interference of scattering light. Outputof the respective unidimensional sensors is used as a reference signalto observe movement of the granular speck pattern as the surface of theobject is moved or distorted. Such movement is photoelectricallydetected at two points and a differential movement between these twopoints is obtained to automatically eliminate a rigid body movementcomponent. This so-called cross correlating method is used to determinea distortion.

According to another method of prior art, a darkroom is used as themeasurement environment and a granular speck pattern generated by thereflecting laser beam is projected on a screen in the form of frostedglass. This projected pattern is picked up by a digital camera or thelike, then a granular speck is selectively extracted by a computer andthe amount of movement of the object in a plane is determined on thebasis of an amount by which a granular point thereof has moved.

A high accuracy is required for the optical parts as well as the opticalsystem mechanism in the case of the method as has been described abovefor calculating an amount of distortion or movement from interferencefringes.

In addition, when a correlative peak value and a reference signal valuedetermined by the cross correlating method is lower than a thresholdvalue, processing is inevitably complicated and becomes troublesome. Themeasurement environment in the form of a darkroom is essential forprojection on the screen formed by frosted glass.

SUMMARY OF THE INVENTION

The present invention aims to eliminate the restriction by manyrequirements for the prior art concerning the construction and themeasurement environment. To achieve this, the present invention aims tosimplify the respective means in the method as well as the apparatus formeasurement and to enlarge a range restricted depending on the type ofthe object to be measured. The method and the apparatus according to thepresent invention should be able to measure even the object moving at ahigh speed by substantially simplifying the image processing incomparison to the prior art.

The object set forth above is achieved by the method and the apparatusaccording to the present invention in which a granular speck pattern isgenerated by a reflecting laser beam as an object to be measured isirradiated with a laser beam. This granular speck pattern is easily anddirectly picked up as an image in a measurement environment like anordinary office and the problem is solved on the basis of a quantitativerelationship between the object and the granular speck pattern generatedby the reflecting laser beam.

The object set forth above is achieved, according to one aspect of theinvention, by a method for measuring an amount at which an object to bemeasured has moved without demand for a particular index or mark innon-contacting fashion, said method comprising steps of irradiating anobject to be measured with a laser beam, optically and directly pickingup the granular speck pattern generated by the reflecting laser beam asan index, calculating the amount of movement on the basis of movement ofthe granular speck pattern with respect to said index and displaying aresult of the calculation as a numerical value of the measured amount ofmovement.

The object set forth above is achieved, according to another aspect ofthe invention, by an apparatus for measuring an amount at which anobject to be measured has moved in plane in non-contacting fashion saidapparatus comprising a laser projector adapted to generate a granularspeck pattern corresponding to a rough surface of an object to bemeasured, a line sensor adapted to directly pick up said granular speckpattern as an index, an A/D converter adapted to convert an analogsignal supplied from said line sensor to a digital signal, a processingunit adapted to calculate an amount of movement of said object on thebasis of movement of the granular speck in said pattern with respect toa pixel interval of said granular speck pattern picked up by said linesensor and represented by said A/D converted signal and a display deviceadapted to display the amount of movement calculated by said processingunit.

The present invention generally comprises four elements. A first elementis to irradiate an object to be measured with a laser beam. A secondelement is to pick up a granular speck pattern generated by reflectionof the laser beam with which the object is irradiated. A third elementis to quantify movement of the object and the picked up granular speckpattern and to use this quantified movement for a specific machine orapparatus. A fourth element is to compare the picked up granular speckpattern with pixels of the line sensor to calculate an amount ofmovement and to display this as a substantial amount of movement.

These elements will be now described in combination with one another.The object is irradiated with the laser beam to generate the granularspeck pattern corresponding to the rough surface of said object. Onearray of random white and black images is continuously picked up by theline sensor as the object moves and a granular speck in said white anddark images is selectively recognized. This speck is followed in a timeseries fashion by the computer and the movement is processed in realtime on the basis of the pixel interval in the line sensor. A numericalvalue of movement obtained in this manner is displayed. For an extremelylarge amount of movement, a granular speck lying within a picking uprange of the line sensor is repeatedly selected as a new indeximmediately before the previously selected granular speck as the indexdeviates from the pick up range of the line sensor. In this way,movement of the object can be continuously measured.

The measuring instrument achieving the present invention comprises asemiconductor laser projector, a line sensor provided with a shieldingtube adapted to shield extraneous light and allowing only the granularspeck pattern to pass therethrough, a video signal branching deviceadapted to branch the video signal picked up by the line sensor in two,a monitor device adapted to display the video signal picked up by theline sensor, an A/D (Analog/Digital) converter, a processing unitcomprising a computer, and a display device adapted to display theamount of movement.

Irradiating the surface of the object to be measured with amonochromatic laser beam of high linearity, luminance, directivity andcoherence generates the granular speck pattern due to coherence of thelaser beam exactly depending on the roughness of the surface irradiatedwith the laser beam.

The granular speck pattern translates as the object contracts and thegranular speck pattern is proportionally reduced or magnified as theobject moves back-and-forth with respect to the measuring instrument.The granular speck pattern generated by the reflecting laser beam isexactly depending on the roughness of the surface irradiated with thelaser beam. In other words, the same granular speck pattern isreproduced when the same position of the object is irradiated with thelaser beam being the same in emission waveform as well as in beamdiameter using same picking up element.

This granular speck pattern is continuously picked up by the line sensoras the index, the analog signal supplied from the line sensor isconverted by the A/D converter to the corresponding digital signal whichis, in turn, input to the processing unit, in which an amount ofmovement of the granular speck pattern in plane is calculated or anamount of back-and-forth movement on the basis of a ratio of reductionor magnification, and a result of calculation is displayed as asubstantial amount by which the object has moved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of the present invention;

FIG. 2 illustrates the granular speck pattern;

FIG. 3 illustrates the granular speck pattern picked up by the linesensor and recognized by a processing unit;

FIG. 4 illustrates the granular speck pattern picked up by the linesensor for an object which is stationary;

FIG. 5 illustrates the granular speck pattern picked up by the linesensor for an object moving in plane;

FIG. 6 illustrates the granular speck pattern picked up by the linesensor for an object moving back and forth; and

FIG. 7 illustrates a method for calculation of the intercentral distancebetween each pair of the adjacent specks.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Before a preferred embodiment of this invention is described inreference with FIG. 1 of the accompanying drawings, details of an objectto be measured and of respective components' types as well as functionswill be described.

Respective reference numerals designate elements as follows: 1—object tobe measured; 2—laser irradiated surface; 3—frosted glass served asscreen; 4—one of white specks in imaged granular speck pattern;5—granular speck pattern; 6—laser beam irradiating the object to bemeasured; 7—laser projector used to generate the granular speck pattern;8—shielding tube adapted to shield extraneous light around the granularspeck pattern; 9—line sensor adapted to pick up each array of granularspeck pattern; 10—video signal branching device adapted to branch videosignal representing the granular speck pattern picked up by the linesensor; 11—monitor means adapted for successive display of video signalrepresenting the granular speck pattern picked up by the line sensor;12—A/D (Analog/Digital) converter adapted to input video signalrepresenting the granular speck pattern picked up by the line sensor toprocessing unit; 13—processing unit adapted to, depending on particularpurpose of application, calculate movement in a plane by using thegranular speck pattern as an index, to calculate back-and-forth movementby calculating magnification or reduction ratio of the granular speckpattern, or to identify the object to be measured by checking up thegranular speck pattern; 14—display device adapted to real time display ameasured movement in plane or back-and-forth movement, or identifiedobject to be measured; 15—measuring instrument having demonstratedfunctional features of method according to the invention.

The line sensor 9 will be able to pick up the granular speck pattern 5so far as an operator can visually recognize any amount of laser beam 6on a surface of the object 1 which is being irradiated with the laserbeam 6. The granular speck pattern 5 is generated depending onirregularity on the surface of the object 1 and such granular speckpattern 5 can be picked up even on the mirror-like finished surface ofan IC wafer or hard disk even if the irregularity is not remarkable.This is true for the surface of the other materials such as wood,metals, paper, cloth, glass or plastics. However, the granular speckpattern 5 cannot be picked up on the surface of fluid material such aswater or mercury. On the surface of coating or adhesive which is in thecourse of being dried or hardened and therefore unable to maintain itsshape, the granular speck pattern 5 is not stabilized at all. Thegranular speck pattern 5 is progressively stabilized as the time elapsesuntil said coating or adhesive is completely dried or hardened.

As has already been described, reference numeral 2 designates thesurface irradiated with a laser beam. Also, reference numeral 3designates the screen in the form of the frosted glass as used in theconventional picking up method. In the measuring environment in the formof a darkroom, the frosted glass 3 is placed in optical path of thereflecting laser so that the granular speck pattern 5 may be projectedon this frosted glass 3 and the image projected in this manner may bepicked up by CCD camera or the like.

As has already been described, reference numeral 4 designates one of thewhite specks in the granular speck pattern 5. Usually it has beendifficult for an operator to visually recognize or to directly pick upthe granular speck pattern 5 in the environment like an ordinary office.When the CCD camera which is commonly available is used to directly pickup the granular speck pattern 5, the granular speck pattern 5 generatedby the laser beam 6 depending on the irregular surface of the object 1is focussed by an image forming lens. Consequently, the image of thelaser beam 6 itself on the object 1 and the granular speck pattern 5cannot be picked up. To overcome this problem, the image forming lensmay be removed from the camera and the reflecting beam may be directlyguided to a CCD element or a line sensor element to achieve picking upof the granular speck pattern 5.

The granular speck pattern 5 is the reflecting laser beam depending onthe irregularity in the surface of the object 1 and it hasconventionally been considered that no granular speck pattern 5 isgenerated on a mirror-like finished surface. However, even on thesurface of the IC wafer which is a typical mirror-like finished surface,the granular speck pattern 5 has recently been picked up in theenvironment like the ordinary office by using the measuring instrument15 (laser emission wavelength: 670 nm, 0.6 mW, at a distance of 30 cmfrom the object 1). In this case, bright and dark contrast of thepattern is deteriorated as the finishing approaches to the degree ofmirror-like finishing.

According to the established theory, the average size of the granularspeck pattern increases, in general, as the diameter of the laser beam 6is reduced, and vice versa. But no variation of the average size isobserved on the mirror-like finished IC wafer, since the surface of theIC wafer is substantially smooth. While the transparent object 1 hasconventionally been considered to be not responsive to irradiation ofthe laser beam to generate the granular speck pattern, glass or film maybe irradiated with the laser beam of high visibility to reliably pick upthe granular speck pattern 5 so far as any amount of laser beam can bevisually recognized on the surface thereof.

A range of irradiation with the laser beam 6 is enlarged as said laserbeam 6 goes away from the laser projector 7. The average area of thegranular speck pattern 5 increases as the object 1 goes away from themeasuring instrument 15 and vice versa.

With the measuring instrument of 670 nm and 0.6 mW, a collective lensmay be moved to vary the beam diameter and to obtain the granular speckpattern 5 having an average area suitable for image processing. Whilethe measuring instrument 15 uses a red laser according to thisembodiment, a green or blue laser beam also may be used to vary theaverage size of the granular speck pattern 5 depending on the particularpurpose of the application.

The shielding tube 8 comprises a tube having a diameter of 10 mm and alength in the order of 5 cm and functions to shield the extraneous lightaround the reflecting laser incident on the line sensor element in thegranular speck pattern 5. This shielding tube 8 may be merely placed infront of the line sensor 9 to shield substantially all extraneous lightdue to, for example, room illumination. Consequently, the granular speckpattern 5 can be directly picked up in an environment like the ordinaryoffice without use of a darkroom as the measuring environment. It hasbeen found that the shielding tube 8 is more effective than an opticalband pass filter adapted to pass the emission wavelength of the laserprojector 7. It should be understood that the granular speck pattern 5can be directly picked up in the environment like the ordinary office byplacing the shielding tube in front of the CCD element of which theimage forming lens has been removed.

The line sensor 9 comprises a plurality of pixels arranged in parallelto the direction in which the object 1 moves and directly picks upmovement of the granular speck pattern 5 through the shielding tube 8.The video signal branching device 10 is adapted to branch the videosignals representing an array of the granular speck pattern 5 picked upby the line sensor 9 into two groups, one of which is input to themonitor means 11 and the other is input to the A/D converter 12.

The monitor means 11 is adapted to time series display the video signalrepresenting the granular speck pattern 5 input from the line sensor 9.As long as the line sensor 9 and the object 1 are stationary, a linearbar code-like image is displayed in the monitor means 11. This bar codebecomes stepped as the object 1 moves and this stepped bar code becomesrelatively flat as the speed at which said object 1 moves increases. Thegranular speck pattern 5 is proportionally enlarged or reduced as theobject 1 moves back-and-forth with respect to the measuring instrument15.

The A/D converter 12 receives the video signal representing the array ofthe granular speck pattern 5 picked up by the line sensor 9 in the formof analog signal via the video signal branching device 10 and convertsthis analog signal to the corresponding digital signal to be input tothe processing unit 13.

The processing unit 13 comprises a microcomputer and processes the videosignal representing the array of granular speck pattern 5 picked up bythe line sensor 9 in a manner depending on particular purpose. Referenceused to calculate movement of the object 1 is the distance between eachpair of the adjacent pixels in the line sensor 9. The line sensor 9 ofthe measuring instrument 15 has 1024 pixels arranged at intervals of 15μm and therefore a measurement accuracy in the order of 20 μm. Thegranular speck pattern 5 displayed in the bar code-like shape becomesstepped as the object 1 is distorted or moved due to its thermalexpansion or tension. A white or black speck in the granular speckpattern 5 appearing immediately before said distortion or movementoccurs may be selectively recognized and the granular speck pattern 5newly supplied from the line sensor 9 may be position compared with saidwhile or black speck to detect said distortion or shift in the directionof movement. Such shift may be calculated as the number of pixels of theline sensor 9, and this number of pixels may be multiplied by the pixelinterval of 15 μm. Then this product may be multiplied by a correctioncoefficient derived from a range to be measured and a laser beamdiameter to determine an amount of distortion or movement. The granularspeck patterns 5 successively supplied from the line sensor 9 may besubjected to the similar processing to determine the amount ofdistortion or movement in real time mode.

Now calculation of the back-and-forth movement will be described (FIG.6). A white or black speck in the granular speck pattern 5 supplied fromthe line sensor 9 immediately before the object 1 moved back-and-forthwith respect to the measuring instrument 15 is selectively recognizedand calculated using the number of pixels of the line sensor 9 asreference. This white or black speck is stored. Then, the number ofpixels constituting the white and black specks in the granular speckpattern 5 newly supplied from the line sensor 9 upon back-and-forthmovement of the object 1 is calculated and compared with said storednumber of pixels. An increased number of pixels suggests that the objectto be measured 1 has moved back from the measuring instrument 15 and adecreased number of pixels suggests that the object 1 has been movedforth toward the measuring instrument 15. An unvaried number of pixelssuggests that no movement has occurred. A correction coefficient may bepreviously established and the increased or decreased number of pixelsmay be multiplied by this correction coefficient to obtain an actualamount of back-and-forth movement. The granular speck patterns 5successively received may be subjected to the similar processing toobtain the amount of back-and-forth movement in real time mode. Whilethe method of obtaining the amount of back and forth movement on thebasis of increased or decreased number of pixels has been describedabove, it is also possible to obtain the amount of back-and-forthmovement on the basis of increased or decreased number of pixels betweenthe center of a white or black speck pixel and the center of the otherwhite or black pixel.

The display device 14 displays an amount of movement so that an operatorcan continuously and visually recognize an array of the granular speckpattern 5 on the basis of which the computer has determined that anobject 1 has moved in plane or back-and-forth. The display device 14 canalso reproduce said array of the granular speck pattern 5.

FIG. 2 shows the granular speck pattern 5 picked up by the CCD camera inthe form of a binary image containing no intermediate color.

FIG. 3 shows the granular speck pattern 5 obtained by picking up saidgranular speck pattern 5 shown in said FIG. 2 by the line sensor 9.

FIG. 4 illustrates the bar code-like granular speck patterns 5successively supplied from the line sensor 9 with respect to the object1 being stationary in time series mode.

Referring to FIG. 5, the video signal 21 represents the object 1 as itsinitial position and the video signal 22 represents the same object 1which has then moved rightward with respect to said video signal 21,i.e., said initial position. The next video signal 23 also has furthermoved rightward but with increasing speed. The following video signal 24indicates that a speed of movement has decreased and said object 1 whichhad continued to move rightward has moved leftward.

FIG. 6 shows that the object 1 has moved back-and-forth (i.e., away andtoward) with respect to the measuring instrument 15. As illustrated, therespective granular speck patterns 5 corresponding to the video signals27 and 28 have expanded with respect to the granular speck pattern 5corresponding to the video signal 26. This means that the object 1 hasreceded from the measuring instrument 15. The granular speck pattern 5corresponding to the next video signal 29 has restored the same state assaid video signal 26, i.e., its initial state.

The granular speck pattern 5 corresponding to the video signal 30 hascontracted from its initial state and indicates that the object 1 hasmoved from the initial position toward the measuring instrument 15. Adistance between the object 1 and the measuring instrument 15 can bedetermined on the basis of a ratio of such reduction or magnification.

Similarly to FIG. 6, FIG. 7 illustrates that the object 1 has movedback-and-forth with respect to the measuring instrument 15. Referring toFIG. 7, the amount of such back-and-forth movement can be determined onthe basis of a varying ratio of the intercentral rectilinear distanceconnecting each pair of the adjacent specks 5. On the basis of the videosignal 31, the video signals 32 and 33 indicate that the object 1 hasreceded from the measuring instrument 15. The video signal 34 is similarto said video signal 31, indicating that the object 1 has restored itsinitial position.

The granular speck pattern 5 corresponding to the video signal 35 hassaid intercentral rectilinear distance contracted with respect to thegranular speck pattern 5 corresponding to the video signal 31. Thedistance between the object 1 and the measuring instrument 15 can bedetermined on the basis of a varying ratio of said intercentralrectilinear distance.

EFFECT OF THE INVENTION

The present invention enables the amount of movement of the object 1 tobe accurately measured in non-contact fashion without demand for aparticular index or mark and in an environment like the ordinary office.Conventionally, the measuring environment in the form of the darkroom,the frosted glass 3 on which the object 1 is projected, high resolutionlenses and the other complex optical system have been essential to pickup the granular speck pattern 5. On the contrary, the present inventionenables the granular speck pattern 5 to be directly picked up as theimage by the line sensor 9 so far as the extraneous light shielding tube8 is placed in front of the element of said line sensor 9. It has beenfound that the range of the granular speck pattern 5 picked up throughthe extraneous light shielding tube 8 placed in front of the CCD(Charge-coupled device) corresponds to the range of the granular speckpattern 5 picked up within the effective area of the CCD through thefrosted glass.

The method according to the present invention may be used to measure ordetermine various factors as follows: movement of the object 1 in aplane on the basis of translation of the granular speck pattern 5;back-and-forth movement of the object 1 on the basis of reduction andmagnification of the granular speck pattern 5; average speed per unittime of said movement in a plane of the granular speck pattern 5; a timepoint at which the object 1 begins or ceases to move on the basis ofmovement of the granular speck pattern 5; a time point at which amirror-like finishing should be terminated by observing whether anaverage area of the granular speck pattern 5 varies or not varies as abeam diameter is varied; and a phase of drying or hardening of coatingor adhesive on the basis of movement of the granular speck pattern.

It will become apparent to those skilled in the art that variousmodifications to the preferred embodiment of the invention as describedherein can be made without departing from the spirit or scope of theinvention as defined by the appended claims.

1. A method for measuring the amount which an object to be measured hasmoved using a granular speck pattern generated by a reflecting laserbeam in non-contact fashion comprising steps of: irradiating an objectto be measured with a laser beam; directly detecting the granular speckpattern generated by the laser beam by a detector in an environment, theenvironment not being a darkroom, and using the detected speck patternas an index; calculating the amount of movement of the object based uponthe movement of a new granular speck pattern corresponding to the movedposition of the object with respect to said index; and displaying aresult of the calculation as a numerical value of the measured amount ofmovement.
 2. The method of claim 1 further comprising moving the objecttoward or away from said detector.
 3. The method as defined in claim 1and further including positioning a light shield in front of saiddetector.
 4. The method as defined in claim 3 wherein said light shielddoes not interfere with said granular speck pattern detected by saiddetector.
 5. An apparatus for measuring the amount which an object to bemeasured has moved using a granular speck pattern generated by areflecting laser beam, said apparatus comprising: a laser projector togenerate a granular speck pattern corresponding to a rough surface of anobject to be measured; a line sensor to directly pick up said granularspeck pattern used as an index; an A/D converter coupled to said linesensor to convert an analog signal supplied from said line sensor to adigital signal; a processing unit coupled to the A/D converter tocalculate the amount of movement of said object on the basis of movementof a granular speck in said granular speck pattern with respect to achange in a pixel interval of said granular speck pattern picked up bysaid line sensor and represented by said A/D converted digital signal;and a display coupled to said processing unit to display the amount ofmovement calculated by said processing unit; wherein the line sensor isable to directly pick up the granular speck pattern in an environmentthat is not a darkroom.
 6. The apparatus as defined in claim 5 andfurther including a light shield positioned in front of said linesensor.
 7. The apparatus as defined in claim 6 wherein said light shielddoes not interfere with said granular speck pattern detected by saiddetector.
 8. The apparatus as defined in claim 7 and further including alight shield positioned in front of said line sensor.
 9. An apparatusfor measuring the amount which an object to be measured has moved usinga granular speck pattern generated by a reflecting laser beam, saidapparatus comprising: a laser projector for generating a granular speckpattern corresponding to the surface of an object to be measured; a linesensor positioned to detect directly said granular speck pattern as anindex; and an electrical circuit coupled to said line sensor forcalculating the amount of movement of said object on the basis ofmovement of a granular speck in said granular speck pattern with respectto a pixel interval of said granular speck pattern picked up by saidline sensor and displaying the amount of movement calculated by saidelectrical circuit; wherein the line sensor is able to directly pick upthe granular speck pattern in an environment that is not a darkroom. 10.The apparatus as defined in claim 9 and further including a light shieldpositioned in front of said line sensor.
 11. The apparatus as defined inclaim 10 wherein said light shield does not interfere with said granularspeck pattern detected by said detector.
 12. The apparatus as defined inclaim 11 and further including a light shield positioned in front ofsaid line sensor.
 13. A method for measuring the amount which an objectto be measured has moved by detecting a granular speck pattern reflectedby a laser beam comprising steps of: irradiating an object to bemeasured with a laser beam; directly detecting a granular speck patterngenerated by the laser beam by a detector in an environment, theenvironment not being a darkroom, and using the detected pattern as anindex; moving the object with respect to said detector; calculating theamount of movement of the object based upon movement of the granularspeck pattern corresponding to the moved position of the object withrespect to said index; and displaying a result of the calculation as anumerical value of the measured amount of movement.
 14. The method ofclaim 13 further comprising moving the object toward or away from saiddetector.
 15. The method as defined in claim 13 and further includingpositioning a light shield in front of said detector.
 16. The method asdefined in claim 15 wherein said light shield does not interfere withsaid granular speck pattern detected by said detector.
 17. An apparatusfor measuring the amount which an object to be measured has moved usinga granular speck pattern generated by a reflecting laser beam, saidapparatus comprising: a laser source for generating a granular speckpattern corresponding to a rough surface of an object to be measured; aline sensor positioned to detect directly said granular speck pattern asan index; a processing unit coupled to said line sensor to calculate theamount of movement of said object on the basis of movement of a granularspeck in said granular speck pattern with respect to a pixel interval ofsaid granular speck pattern detected by said line sensor; and a displaycoupled to said processing unit to display the amount of movementcalculated by said processing unit; wherein the line sensor is able todirectly pick up the granular speck pattern in an environment that isnot a darkroom.
 18. The apparatus as defined in claim 17 and furtherincluding a light shield positioned in front of said line sensor. 19.The apparatus as defined in claim 18 wherein said light shield does notinterfere with said granular speck pattern detected by said detector.20. The apparatus as defined in claim 19 and further including a lightshield positioned in front of said line sensor.
 21. An apparatus formeasuring the amount which an object to be measured has moved using agranular speck pattern generated by a reflecting laser beam, saidapparatus comprising: a collimated light source for generating agranular speck pattern corresponding to the surface of an object to bemeasured; a line sensor positioned to detect directly said granularspeck pattern as an index; and an electrical circuit coupled to saidline sensor for calculating the amount of movement of said object on thebasis of movement of a granular speck in said granular speck patternwith respect to a pixel interval of said granular speck pattern pickedup by said line sensor and displaying the amount of movement calculatedby said electrical circuit; wherein the line sensor is able to directlypick up the granular speck pattern in an environment that is not adarkroom.
 22. The apparatus as defined in claim 21 and further includinga light shield positioned in front of said line sensor.
 23. Theapparatus as defined in claim 22 wherein said light shield does notinterfere with said granular speck pattern detected by said detector.24. The apparatus as defined in claim 23 and further including a lightshield positioned in front of said line sensor.